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Atomic Energy
We already looked at ways energy can be expressed and transferred
from one form to another
Heat
Light
Sound
Electrical
Magnetic
Mechanical
Chemical
In-fact, the above forces that we experience every day are really due to
four more fundamental forces in nature that operate at the atomic level.
Atomic Energy
Four fundamental interactions are conventionally recognised: gravitational,
electromagnetic, strong nuclear, and weak nuclear.
Everyday phenomena of human experience are mediated via gravitation and
electromagnetism.
The strong interaction, synthesising chemical elements via nuclear fusion within
stars, holds together the atom's nucleus, and is released during an atomic
bomb's detonation.
The weak interaction is involved in radioactive decay.
Atomic Energy
We get atomic energy from the interaction of .....
The weak nuclear force
which causes Alpha , Beta and Gamma radiation.
The strong nuclear force
that sticks the Protons and neutrons together in the nucleus of the atom.
Atomic Energy - Fission
If you bust open the nucleus of an atom the
energy that was sticking the protons and neutrons
together (strong nuclear force), is released and
transferred into light and heat. Lots of it!
When we bust open the nucleus we call that
Fission – To slit into two pieces.
The bigger the nucleus the more light and heat.
Atomic Energy - Fission
The best atoms to use are big fat ones that have lots of Protons and
Neutrons in their nucleus and are already a bit unstable.
The greater the ratio of Protons to Neutrons the more unstable they are.
These nuclei also give of lots of Alpha and Beta radiation.
Unfortunately these elements are rare. Most of the really big fat atoms
were made in the lab under conditions that you don't find in nature.
There are only a couple of elements we can dig up in enough quantity to
use as fuel in a nuclear reaction.
Atomic Energy - Fuel
Uranium 235
One of the only naturally occurring elements that is unstable enough to allow
itself to be split. It's nucleus has 92 protons and 143 neutrons.
It's found mixed in with Uranium 238, a more common isotope. To make
nuclear fuel you have to increase the amount of U235 in the mix. This is called
enrichment
Atomic Energy - Fission
A single neutron is captured and destabilises and already unstable nucleus.
Three neutrons are released along with huge amounts of heat and light.
It's almost exactly like a game of billiards
Atomic energy- fission reaction
The Fission Reaction.
(Cannon shot)
Pack very many U235 atoms
in to a small space. Fire off a
few random neutrons. Stand
back (a long way back) and
watch the fun. As each
nucleus splits it fires off an
additional 3 neutrons that
split any U235 atoms that are
close by. Lots and lots of
heat is given off. Lets look at
a Simulation.
The Reactor
In a nuclear reactor we pack a bunch of uranium metal rods in a can.
Between each rod is another rod made of Graphite. They are called
control rods. These graphite rods soak up Neutrons. Pull the rods out
and these Neutrons that are whizzing around can then smash up the any
U235 atoms close by. The reactor core gets hot (critical mass).
Generating power
Simple really. U235 atoms get smashed up. The core gets hot. We boil some
water and turn it into high pressure steam. The high pressure steam turns a
turbine wheel which is attached to a generator. Bingo electricity. We have a
chain of energy conversion resulting electricity!
The chain of energy conversion
Nuclear fission (atomic) – High pressure steam (thermal/mechanical) – Rotating
Turbine (mechanical) – Generator (mechanical) – Electricity (electromagnetic)
Nuclear power plant